Celluloid is primarily produced through mixing of industrial grade nitrocellulose (NC) and camphor in the presence of suitable solvents like ethanol and acetone. U.S. Pat. No. 8,696,838 issued to Niloufar Faridi et al (the '838 patent) describes mixing nitrocellulose and camphor to produce celluloid. The bulk celluloid material is then processed by straining, roll milling, and “hiding” into desired sheets of celluloid. A typical process for preparing the celluloid sheets starts with selecting a certain number of “hides” which are then blocked and fused at a desired pressure and temperature. The blocks are then sliced into sheets at a desired thickness after a conditioning period. Alternatively, celluloid can be manufactured by “film casting,” which involves mixing nitrocellulose, camphor, and other ingredients; and subsequently casting and drying the bulk mixture into a film of a desired thickness. These sheets of celluloid, however, cannot be easily formed into large complex geometries or efficiently stored. Thus, a need exists for a spherical celluloid bead material for ease of processing and storage.
There are several mechanical means to prepare bead-like celluloid material. One method is to pin-punch celluloid sheets to produce “chads” of celluloid bead material. The chads are cylindrical in shape and difficult to achieve at sizes below 1.5 mm×0.8 mm. Alternatively, sheets of celluloid material may also be ground and pulverized. The resulting material, however, are irregular in shape with rough edges and angled surfaces requiring further milling, which is time consuming and inefficient. Bead-like celluloid may also be prepared by an extrusion process similar to propellant manufacturing techniques as disclosed in the '838 patent. This process mixes all the ingredients in a batch mixer with solvents. NC and a plasticizer, preferably camphor, are mixed in an organic solvent, such as ethanol and/or acetone along with a stabilizer and a chemical blowing agent. Once a dough-like mix is formed, the material is blocked in a standard hydraulic block press and extruded through a die with desired dimensions in a form of strands, similar in shape to spaghetti. These strands are then cut to a desired length, targeting a length to diameter (L/D) ratio of close to one.
While these mechanical celluloid bead processing techniques have been shown to be effective, they are time consuming and result in lower than optimal yield. These methods also do not achieve an ideal spherical geometry. Therefore, a need exists to prepare celluloid beads that overcome such drawbacks.